Tucson is a city in and the county seat of Pima County, Arizona, United States, and is home to the University of Arizona. It is the second-largest city in Arizona behind Phoenix, with a population of 542,629 in the 2020 United States census, while the population of the entire Tucson metropolitan statistical area (MSA) is 1,043,433. The Tucson MSA forms part of the larger Tucson-Nogales combined statistical area. Both Tucson and Phoenix anchor the Arizona Sun Corridor. The city is 108 miles (174 km) southeast of Phoenix and 60 mi (100 km) north of the United States–Mexico border.

The Arizona Sun Corridor, shortened Sun Corridor, is a megaregion, or megapolitan area, in the southern area of the U.S. state of Arizona. The Sun Corridor is comparable to Indiana in both size and population. It is one of the fastest growing conurbations in the country and is speculated to double its population by 2040. The largest metropolitan areas are the Phoenix metropolitan area – Valley of the Sun, and the Tucson metropolitan area – The Old Pueblo. The regions' populace is nestled in the valley of a desert environment. Similar to Southern California, the urban area extends into Mexico, reaching the communities of Heroica Nogales and Agua Prieta.